Guide blade arrangement for an axial turbo-machine

ABSTRACT

A guide blade arrangement for an axial turbo-machine is provided. The guide blade arrangement includes at least one annular guide blade carrier and an inner ring arranged concentrically with respect to the guide blade carrier, between which guide blade carrier and inner ring a number of guide blades are arranged in a radial configuration. To obtain a low-wear and particularly durable fastening of the guide blade, which is supported by the guide blade carrier, to the inner ring, it is proposed that the guide blades are fastened resiliently to the inner ring. Here, the fastening is provided by means of a spring element. By means of the spring element, it is possible to ensure a uniform contact pressure of the guide blade head against the inner ring or if appropriate against a further spring element, such that occurring stresses and wear can be reduced.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US National Stage of International ApplicationNo. PCT/EP2009/064427, filed Nov. 2, 2009 and claims the benefitthereof. The International Application claims the benefits of EuropeanPatent Office application No. 08021215.2 EP filed Dec. 5, 2008. All ofthe applications are incorporated by reference herein in their entirety.

FIELD OF INVENTION

The invention refers to a stator blade arrangement for an axialturbomachine, comprising an annular stator blade carrier and an innerring which is arranged concentrically to the stator blade carrier,between which a number of stator blades, with a blade airfoil, arearranged in a radial configuration, wherein each stator blade isfastened on the stator blade carrier.

BACKGROUND OF INVENTION

A stator blade arrangement which is referred to in the introduction issufficiently known from the prior art. This is known for example in thecase of compressors of stationary gas turbines, in which stator bladesof the compressor are fastened on a stator blade carrier or on acompressor casing. For this purpose, known stator blade carriers, whichin particular are mostly formed with a tubular shape, have retainingslots with undercuts which extend on their inner generated surfaces inthe circumferential direction and in which stator blades or outer ringsare inserted and fastened. The stator blades in this case on the onehand can be formed as free-standing stator blades so that their bladeairfoil tips lie opposite an inner boundary wall of the flow path of thecompressor, forming a gap. It is also known, for example from US20007/0177973 A1, that the inner boundary wall of the flow path is partof the stator blades or can be retained by the stator blades themselves.In this case, the known stator blades either have shrouds which arearranged in each case on the tip side, which then form parts of theboundary wall, or the stator blades carry an inner ring on the tip side,the outer generated surface of which then constitutes the inner boundaryfor the flow path. The fastening of the inner ring on the stator bladesof the stator blade arrangement in this case can be carried out via asuitable bolted connection, by means of welding, or else by means ofcaulking.

In the case of the known types of fastening of the inner ring on thestator blades of the stator blade arrangement, wear or crack emergenceon the connection of inner ring and stator blade can occur duringoperation of the compressor. The wear phenomena occur due to rotation ofthe inner ring as a result of the aerodynamic blade load and/or due tothermally induced expansions which occur as a result of the heat whichis generated during compression in the compressor. Periodic blade loadchanges or vibrations can also lead to wear phenomena.

In addition, a radially inner sprung fastening of the blade airfoils isknown from publications GB 2 400 415 A and U.S. Pat. No. 2,914,300.

The object of the invention is consequently the provision of a statorblade arrangement, which is referred to in the introduction, for anaxial turbomachine, which enables a particularly simple,expansion-tolerant, low-wear and reliable fastening of stator blades onan inner ring.

SUMMARY OF INVENTION

The object which forms the basis of the invention is achieved by meansof a stator blade arrangement according to the features of the claims.

According to the invention, it is provided that in the case of thestator blade arrangement which is referred to in the introduction thestator blade comprises a stator blade tip with a web and with a tipsection which extends transversely to it, the stator blade tipprojecting into an encompassing slot of the inner ring, and the slot isclosed off in each case by a shroud in the section between two adjacentstator blades, that adjacent shrouds are at a distance from each other,forming recesses which accommodate the webs, and that the stator bladetip of at least one of the stator blades is spring-fastened on the innerring by means of at least one spring element which is arranged in a sideface of the recess which faces the web in question.

The invention is based on the knowledge that a rigid connection ofstator blades on the inner ring is disadvantageous. It accordinglyproposes a type of connection which to a small extent enables relativemovements of stator blades to the inner ring in a wear-free manner,without damage to the connection. Consequently, the invention departsfrom the previous procedures in which a rigid, fixed connection betweenstator blades and inner ring was provided.

In the course of the invention, a simple spring element is now to beused for fixing the stator blade on the inner ring. By using a springfastening of stator blades on the inner ring a uniform pressing of thestator blade in question on the inner ring can be carried out, whichefficiently minimizes occurring stresses which are created as a resultof thermal expansions and/or static and/or dynamic stresses. At the sametime, as a result of the spring-fastening the installation tolerances,which are necessary for a simple installation, can be especially simplycompensated.

By reducing wear and avoiding cracks, an increase of the plantavailability can be altogether enabled since checks and reworking ofworn components, which have been necessary up to now, are discontinuedwhen applying the invention. Furthermore, repair costs can be saved andintermediate inspections can possibly be dispensed with. Moreover, thedescribed measure can easily be combined with some of the knownsolutions from the prior art, which represents an improved repairpossibility of existing turbomachines.

Each stator blade in question, on the inner ring side, comprises astator blade tip, which is recessed in the inner ring, i.e. projectsinto a slot which is provided for it, and by means of which the statorblade is spring-fastened on the inner ring. So that the stator blade inquestion can be spring-fastened on the inner ring, it comprises at leastone construction element, namely the stator blade tip, which can beconnected to the inner ring and is suitable for carrying this.

According to a simple development, the stator blade tip of each statorblade in question comprises a web which is arranged in each case in anoutwardly open recess which is arranged on the inner ring and in which aspring element is arranged in at least one of the side faces of therecess which faces the web in question, and which spring element abutsin a pretensioned manner against the inner ring and against the web ofthe stator blade in question. Therefore, for spring-fastening of thestator blade on the inner ring provision is made for a furtherconstructional component, that is to say the spring element, which onone side is supported on the inner ring and on the other side issupported on the web of the stator blade in question. In this case, thestator blade arrangement is designed so that the spring element ispreferably pretensioned and therefore presses the web of the statorblade in question either indirectly or directly onto the inner ring, indetail onto one of the two side faces of the recess.

The stator blade tip is formed in the shape of an inverted T by means ofthe web and a tip section which extends transversely to it, wherein theweb connects the tip section to an aerodynamically curved blade airfoilof the stator blade in question, and wherein the inner ring has anencompassing slot, which is fanned corresponding to the stator bladetip, for accommodating the stator blade tips, which slot is closed offin each case by a shroud in the section between two adjacent statorblades, that is to say towards the blade airfoil. As a result of thefaun-fitting connection of the stator blade to the inner ring by meansof the inverted T-shaped stator blade tip or stator blade hook which isarranged on the stator blade, and a slot which is provided on the innerring and which is formed corresponding to the shape of the stator bladetip, a stator blade arrangement can be disclosed in which the inner ringis especially reliably carried by the stator blades. This development isespecially advantageous when the stator blade arrangement itself, theinner ring and/or the annular stator blade carrier, is not formed in onepiece in each case but are faulted by means of at least two arc-shapedring segments which during installation and/or removal are separated ineach case from the other ring segments in a manageable manner. Theshroud on the one hand prevents displacement of the inner ring inrelation to the stator blades along the circumference since the shroudis arranged in each case between two stator blades and therefore blocksthe displacement path along the slot. On the other hand, the shroud alsoensures a stepless boundary surface of the flow passage. Altogether, thecomponents of the arrangement and the arrangement itself can then beeasily produced.

Advantageous developments are disclosed in the dependent claims.

According to an advantageous development, two spring elements, which arearranged on side faces of the recess which lie opposite each other, areprovided for each stator blade in question. As a result of this, eachstator blade which is mounted in such a way indirectly, that is to sayvia the spring elements, is arranged on the inner ring in a pretensionedstate. The spring force of each spring element in this case isexpediently oriented in the circumferential direction of the inner ring.If a tension sleeve is used as a spring element, there is only a linearcontact between the web of each stator blade in question and the tensionsleeve, as a result of which the static loading of the stator blade onthe connecting point is lower than in the case of a two-dimensionallyfixed stator blade. Since the static loading is carried out primarily asa result of an occurring displacement of the inner ring in thecircumferential direction caused by an aerodynamic blade loading, adisplacement-tolerant fastening in the form of a spring-mounting in thecircumferential direction is necessary in order to avoid wear and crackemergence and crack propagation.

It can be of advantage to a simple production of the stator bladearrangement if the inner ring comprises two ring sections which can beinstalled after their assembly to form a one-piece inner ring.

If the stator blade arrangement is used especially in stationaryturbomachines, it is advantageous if the stator blade arrangement itselfcomprises two or more ring segments, that is to say that the inner ringand/or the annular stator blade carrier are formed as arc-shaped ringsegments. Since the stator blade arrangement and its components are partof the rotationally fixed component parts of a turbomachine, which, ifused in the stationary region, have a parting plane, as a result ofwhich the rotationally fixed component parts are split for an upper anda lower half, a stator blade arrangement which is split into two ringsegments, each of 180°, is particularly suitable for stationaryturbomachines. A simple installation of the individual components,forming an altogether annular stator blade arrangement, is thenpossible. The stator blade arrangement is preferably used in aturbomachine which can be formed especially as an axial compressor oraxial turbine. Moreover, the stator blade carrier can be arranged insidea separate casing or even itself can be formed as a casing.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained with reference to a drawing. Furtheradvantages and further features result in this case from the figuredescription.

In the drawing:

FIG. 1 shows a segment 10 of a stator blade arrangement 12 of an axialturbomachine in a perspective view;

FIG. 2 shows an exploded view of FIG. 1;

FIG. 3 shows a longitudinal section through a connection according tothe invention of stator blade and inner ring;

FIG. 4 shows a detail of the inner ring without stator blade;

FIG. 5 shows a side view according to the section V-V, and

FIGS. 6, 7 schematically show the twist of the stator blade as a resultof load reaction and support reaction for a stator blade which isfastened according to the prior art and for a stator blade which isfastened according to the invention.

DETAILED DESCRIPTION OF INVENTION

FIG. 1 shows a segment 10 of a stator blade arrangement 12 of an axialturbomachine in a perspective view. The segment 10 is formed in theshape of an arc and spans an arc of 180°. Two of the segments 10 whichare shown in FIG. 1 can be assembled to form a stator blade arrangement12 according to the invention, which is then formed in an annularconfiguration. Slots 18 which extend in the axial direction and are foraccommodating stator blades 20 are provided on an inner face 16 of thestator blade carrier 14. In FIG. 2, the stator blades 20 which are to beinserted in the slots 18 are shown displaced to the stator blade carrier14 on account of the exploded type of view. The radially outer part ofthe stator blade 20 in this case is referred to as a stator blade rootin each case and the radially inner part of the stator blade 20 isreferred to as a stator blade tip. Between stator blade root and statorblade tip the stator blade 20 has an aerodynamically curved bladeairfoil. An inner ring 22, of which only a 180° segment is shown in FIG.2, is arranged on the stator blades 20 on the tip side. The inner ring22 or its segments are assembled in this case from two ring sections 36,38 or ring section segments.

The stator blade arrangement 12 which is to be assembled from twosegments 10 therefore comprises a ring of stator blades 20 which is alsoknown as a stator blade ring and can be part of a compressor stage orturbine stage.

The stator blade carrier 14 is fastened on a casing, which is notadditionally shown, of the axial turbomachine, for example of acompressor, or itself is formed as a casing. The stator blade carrier 14carries the stator blades 20 which are fastened on it on the inside andwhich in their turn carry the inner ring 22 inside on the tip side. Theouter generated surface of the inner ring 22 and the inner surface 16 ofthe stator blade carrier 14 in this case form the radial inner and outerboundary for a medium which flows through the axial turbomachine. If theaxial turbomachine is formed as a compressor, the medium is compressedair, or air which is to be compressed.

FIG. 3 shows a longitudinal section (in the sense of the axialturbomachine) through a connection according to the invention of thestator blade 20 to the inner ring 22. The blade airfoil 28 which is partof the stator blade 20 is only partially shown. A stator blade tip 30,which has a web 32 and also a tip section 34 which extends transverselyto it, is provided on the blade airfoil 28 on the tip-side section ofthe stator blade 20. By means of the web 32 and the tip section 34, thestator blade tip 30 altogether has an inverted T-shape, as seen in crosssection.

The inner ring 22 is provided with an outwardly open slot 44, thelongitudinal sectional contour of which is formed corresponding to thestator blade tip 30. The inner ring 22 comprises the two ring sections36, 38 which in their turn according to FIG. 2 are also formed as 180°arc-shaped segments. The ring sections 36, 38 or their segments areinterconnected in a fixed manner via a weld joint 40. The ring sections36, 38 have in each case projections 42, 43 which are oriented towardseach other, in each case for forming an undercut by means of which theinverted T-shaped stator blade tip 30 can be radially fixed.

FIG. 4 shows a perspective view of a section of the inner ring 22, inwhich the ring sections 36, 38 for reasons of clarity are not shown intheir final constructional position but apart. In their finalconstructional position the two projections 42, 43, as far as possible,abut against each other without a gap. In the projection 43 of the ringsection 36, a recess 46, of which two are shown in FIG. 4, is providedfor each stator blade 20. The recesses 46 serve for accommodating theweb 32 of the stator blade tip 30 of the stator blade 20. The projection43 therefore forms a shroud 47 between the recesses which closes off theslot 44 between two stator blades 20 in order to provide amisalignment-free flow path. Between two adjacent shrouds 47, therefore,a recess 46 is provided in each case in which the web 32 is accommodated(FIG. 3). For overview reasons, the stator blade 20 which is shown inFIG. 3 is not shown in FIG. 4. Each recess 46 has two side faces 48which lie opposite each other. In at least one of the two side faces 48of each recess 46 a further pocket 50 is provided in which a springelement 52, which is formed as a tension ring, is provided forspring-fastening of the stator blade 20 on the inner ring 22. In FIG. 4,a spring element 52 is schematically shown only in the recess 46 whichis shown there further to the left. FIG. 5 shows a side view of theportion of the ring section 36 which in FIG. 4 is shown further to theright. This recess 46 is delimited by two side faces 48 in which apocket 50 is provided in each case. The pocket 50 is formed essentiallyin the shape of a circle segment and extends over the entire axiallength of the recess 46. The pocket 50 in this case for example may havebeen produced by drilling or eroding before introducing the recess 46.The pocket 50 in this case is arranged so that the diameter of thepocket 50, which lies in the radial plane of the axial turbomachine, isarranged in the projection 43 or in the shroud 47 so that only acomparatively small section of the hole circle is covered by the recess46. The tension sleeve then has a diameter which is only slightlysmaller than the diameter of the pocket 50. As a result of the selectedposition of the pocket 50, the spring element 52 which is formed as atension sleeve can still project by such a distance into the recess 46that the web 32 located there, which is not shown in FIG. 5, is seatedwith spring effect on the inner ring 22 via the spring element 52. Onaccount of the selected arrangement of the recess 46, the pockets 50 andthe spring elements 52, the force direction of the last-mentioned actsin the circumferential direction.

Falling out of the spring element 52 from the pocket 50 into the recess46 can be avoided on account of the position of the pocket 50. Thisfacilitates the assembly of the stator blade arrangement 12.

Naturally, the spring element 52 could also be mounted in pockets whichare arranged on the web 32 and not on the side faces 48 of the recess46.

FIG. 6 and FIG. 7 schematically show the twist of the stator blade 20 asa result of load reaction and support reaction for a stator blade whichis fastened according to the prior art (FIG. 6) and for a stator bladewhich is fastened according to the invention (FIG. 7).

Since a stator blade 20 which is fastened on the tip side according tothe prior art is twisted to a particularly high degree, high loads andwear, which depending upon load can lead to crack emergence and crackpropagation, could especially occur at their weakest point, namely onthe stator blade tip 32 or else on the inner ring. With the invention, aspring-fastening of the stator blade tip 30, and therefore a fasteningwhich is to be referred to as a flexible bearing, is now proposed whichleads to significantly lower twist of the stator blade 20 as a result ofload reaction and support reaction. As a result of this, the loading onthe stator blade tip 32 can be reduced which delays or prevents theemergence of cracks and wear. In particular, the displacement of theinner ring in the circumferential direction which occurs as a result ofaerodynamic blade loading creates a static loading of the blade whichcan be better compensated by means of the connection according to theinvention than stator blades which are fastened according to the priorart.

In total, the invention refers to a stator blade arrangement 12 for anaxial turbomachine and comprises at least one annular stator bladecarrier 14 and an inner ring 22 which is arranged concentrically to thestator blade carrier 14, between which a number of stator blades 20 arearranged in a radial configuration. In order to disclose a low-wear andparticularly durable fastening of the stator blade 20, which is carriedby the stator blade carrier 14, on the inner ring 22, it is proposedthat the stator blades 20 be spring-fastened on the inner ring 22. Thefastening is carried out in this case by means of a spring element 52.By means of the spring element 52, a uniform pressing of the statorblade tip 30 onto the inner ring 22, or possibly onto a further springelement 52, can be ensured so that stresses and also wear which occurcan be reduced.

1.-11. (canceled)
 12. A stator blade arrangement for an axialturbomachine, comprising: an annular stator blade carrier; an inner ringwhich is arranged concentrically to the stator blade carrier; and aplurality of stator blades arranged between the annular stator bladecarrier and the inner ring and arranged in a radial configuration,wherein each stator blade comprises a blade airfoil and is fastened onthe stator blade carrier, wherein each stator blade comprises a statorblade tip, with a web and with a tip section which extends transverselyto the web, and which projects into an encompassing slot of the innerring, and the slot is closed off in each case by a shroud in a sectionbetween two adjacent stator blades, wherein adjacent shrouds are at adistance from each other, forming a plurality of recesses whichaccommodate the plurality of webs, and wherein the stator blade tip ofat least one of the stator blades is spring-fastened on the inner ringby means of a spring element which is arranged in a side face of arespective recess which faces the web.
 13. The stator blade arrangementas claimed in claim 12, wherein the spring element abuts in apretensioned manner against the inner ring and against the web of therespective stator blade.
 14. The stator blade arrangement as claimed inclaim 12, wherein two spring elements, which are arranged on side facesof the recess which lie opposite each other, are provided for eachstator blade.
 15. The stator blade arrangement as claimed in claim 12,wherein the spring element is formed as a tension sleeve.
 16. The statorblade arrangement as claimed in claim 12, wherein a pocket foraccommodating the spring element, from which the spring elementpartially projects, is provided in the respective side faces.
 17. Thestator blade arrangement as claimed in claim 12, wherein a spring forceis oriented in a circumferential direction of the inner ring.
 18. Thestator blade arrangement as claimed in claim 12, wherein the inner ringcomprises two ring sections.
 19. The stator blade arrangement as claimedin claim 12, wherein the inner ring and the annular stator blade carriercomprises at least two ring segments.
 20. The stator blade arrangementas claimed in claim 12, wherein the inner ring or the annular statorblade carrier comprises at least two ring segments.
 21. The stator bladearrangement as claimed in claim 12, wherein the stator blade carrier isformed as a casing.
 22. A turbomachine, comprising: a stator bladearrangement, comprising: an annular stator blade carrier, an inner ringwhich is arranged concentrically to the stator blade carrier, and aplurality of stator blades arranged between the annular stator bladecarrier and the inner ring and arranged in a radial configuration,wherein each stator blade comprises a blade airfoil and is fastened onthe stator blade carrier, wherein each stator blade comprises a statorblade tip, with a web and with a tip section which extends transverselyto the web, and which projects into an encompassing slot of the innerring, and the slot is closed off in each case by a shroud in a sectionbetween two adjacent stator blades, wherein adjacent shrouds are at adistance from each other, forming a plurality of recesses whichaccommodate the plurality of webs, and wherein the stator blade tip ofat least one of the stator blades is spring-fastened on the inner ringby means of a spring element which is arranged in a side face of arespective recess which faces the web.
 23. The turbomachine as claimedin claim 22, wherein the turbomachine is formed as an axial compressoror an axial turbine.
 24. The turbomachine as claimed in claim 22,wherein the spring element abuts in a pretensioned manner against theinner ring and against the web of the respective stator blade.
 25. Theturbomachine as claimed in claim 22, wherein two spring elements, whichare arranged on side faces of the recess which lie opposite each other,are provided for each stator blade.
 26. The turbomachine as claimed inclaim 22, wherein the spring element is formed as a tension sleeve. 27.The turbomachine as claimed in claim 22, wherein a pocket foraccommodating the spring element, from which the spring elementpartially projects, is provided in the respective side faces.
 28. Theturbomachine as claimed in claim 22, wherein a spring force is orientedin a circumferential direction of the inner ring.
 29. The turbomachineas claimed in claim 22, wherein the inner ring comprises two ringsections.
 30. The turbomachine as claimed in claim 22, wherein the innerring and/or the annular stator blade carrier comprises at least two ringsegments.
 31. The turbomachine as claimed in claim 22, wherein thestator blade carrier is formed as a casing.